We have this same set up in our cars. Ours have a clamp for the fatter M4 handguards. The LWRC quad rails we have fit in the clamp. My LWRC comes with factory railskins that seem pretty thin but there is plenty of room inside the clamp. If you are not in a hurry, Monday I will bring in a personal rifle with a MOE forearm and try that. I also have a few weapons with Knights rails and I will try them to. No more take home so I got to wait until I get back to work. David
Thanks again for all the additional replies. dwhitehorne, I look forward to hearing how other set ups fit. OTO27, I have an assigned car, but I will keep your advice in mind. Based on everything I’ve seen so far, I’m thinking and FSB mount will probably end up being the way I go.
If a MOE handguard fits, this is a sanitary way to mount a light to the MOE handguard.
The part is from Impact Weapons Components.
In case you don’t recognize, the part under the FSB is a Colt side sling swivel.
The IWC part only touches the weapon at the two Allen-drive fasteners.
Thank You.
That pic answered a question. It will clear a SSA.
Many around here drill a couple of holes in the handguard at 10 or 2 o’clock close to the fsb and attach a small “weaver” rail.
What handguard will your rack accept, CAR, M-4 or both? I can measure them and the dimensions of various rails to see what will fit.
The magpul moe is not as wide as the standard hand guards on a 6920. The Troy TRX is a more narrow handguard as well. The santa cruz locks are the way to go
Brownells will pretty much let you return anything for a refund for any reason. It may be a good call to try some MOE handguards. Yes, they will give you a LE discount, too.
Deciding what handguards you are gong to use based on how they fit in a rack is flawed logic.
I would look at modifiying the rack.
That’s someone who’s never had to deal with a separate fleet section. 
Our department uses Troy MRF Drop-In rails, they fit perfectly in our Big Sky mounts. We mount our Streamlights TLR-1’s on the 6 o’clock rail and they still fit in our mounts. I also use a Troy Industries sling mount as a hand stop/switch guard for the light.
OP sorry for the delay, I’ve been looking for 2 days for the rack you have pictured since we use the same rack. I couldn’t find one in the area I am in now so here are some pictures of the proguard which is the same size clamp you have pictured. The one for the fat M4 handguards. Hope this helps. David
MOE on my personal parts gun. Plenty of wiggle room but I had to remove the light I had mounted. Mostly because the rack is adjusted for the LWRC.
LWRC M6A1S with the factory rail skins
M4A1 with Surefire rails. I usually run a Knights cover on the bottom and ladders on the sides. Fits fine like that but I was too lazy to find some other Knights covers for the sides.
Knights rail on a M4A1 fits about like the Surefire rail.
Here is the empty rack for shotgun and rifle
